As there are a constantly growing number of mobile data services, frequency band resources appear more and more insufficient, and a demand for a large number of mobile data services may not be satisfied by deploying a network and transmitting the services only over licensed frequency band resources, so transmission of the mobile data services may alternatively be deployed over unlicensed frequency band resources so as to increase the utilization ratio of the frequency band resources, and to improve experiences of users, where a mobile data service is transmitted in an unlicensed frequency band which is a secondary carrier with the assistance of a primary carrier in a licensed frequency band.
The unlicensed frequency bands can be shared by various wireless communication systems, e.g., Bluetooth, Wireless Fidelity (WiFi), and other systems, all of which access the shared unlicensed frequency band resources by competing for the resources, so coexistence between Unlicensed Long Term Evolution (simply U-LTE or LTE-U) systems deployed by different operators, and between the LTE-U systems, and the WiFi and other wireless communication systems has been studied as a focus.
The LTE system supports two duplex modes of Frequency Division Duplex (FDD) and Time Division Duplex (TDD) to which there are different frame structures applicable. The two frame structures are common in that each radio frame includes 10 sub-frames of 1 ms. A first type of frame structure applicable to the FDD system is as illustrated in FIG. 1, and a second type of frame structure applicable to the TDD system is as illustrated in FIG. 2.
As can be apparent from the LTE frame structures, data are transmitted in both of the frame structures in the unit of a sub-frame with a length of time which is 1 ms, but in the LTE-U system, due to contention based access in the Listen Before Talk (LBT) mode, a period of time for an eNB to prepare for data, a period of time for the eNB to prepare for a radio frequency, and other factors, an LTE-U signal may be transmitted starting in time at such any location in some sub-frame that the incomplete sub-frame is transmitted, that is, the length of time of the physical resource is less than the length of a normal sub-frame. If no signal is transmitted in the incomplete sub-frame, then the resource will be preempted by one of the other nodes intensively competing for the resource.
Since the LTE-U system is designed to guarantee fair competition between the LTE-U system and the Wi-Fi system, a period of time for the LTE-U system to transmit once is appropriately 10 ms, and preferably no more than 40 ms. If the LTE-U system transmits once for a period of time of at most 10 ms, then the systems will compete for an access in such an incomplete sub-frame that the sub-frame available as a result is also the incomplete sub-frame. If no data are transmitted in either of two incomplete sub-frames, then the efficiency of transmission in the LTE-U system will be degraded by a factor of at least 10%. If the LTE-U system transmits once for a period of time of at most 4 ms, and no data are transmitted in either of two incomplete sub-frames, then the efficiency of transmission in the LTE-U system will be degraded by a factor of at least 25%, so if no data are transmitted in any incomplete sub-frame, then it will be unacceptable from both the perspective of resource utilization and the technological perspective. Accordingly if an incomplete sub-frame is transmitted over a resource over which a complete sub-frame fails to be transmitted, and data are transmitted in the incomplete sub-frame, then the efficiency of data transmission will be improved, and the resource can be avoided from being wasted. There has been absent an integrated solution to transmission of data in an incomplete sub-frame in an unlicensed frequency band in an LTE system.
In summary, there has been absent in the prior art a solution to transmission of data in an incomplete sub-frame in an unlicensed frequency band.